This is a continuation of application Ser. No. 11/172,490 filed Jun. 29, 2005 now U.S. Pat. No. 7,276,973.
1. Field of the Invention
The present invention is generally in the field of electrical circuits. More particularly, the invention is in the field of power amplifiers.
2. Background Art
Power amplifiers, such as linear power amplifiers used in cellular handsets, are required to maintain a minimum specified linearity, which is defined by the Federal Communications Commission (“FCC”) or by customer specifications. Since linear power amplifiers, such as linear power amplifiers used in cellular handsets as well as other wireless applications typically consume a significant amount of battery power, they are generally designed to draw the least amount of current possible. However, the goal of minimum current consumption must be achieved while meeting the minimum specified linearity requirements. Since it is difficult to meet linearity requirements at the highest output power that the linear power amplifier is required to deliver, a conventional linear power amplifier used in cellular handsets is typically optimized so that it meets the linearity requirement at the highest output power level while consuming the least amount of current. As a result, the conventional linear power amplifier can significantly exceed the minimum specified linearity requirements at low output power levels.
However, since there is typically a tradeoff between current consumption and linearity (i.e. an increase or decrease in linearity is typically accompanied by a respective increase or decrease in current consumption), the conventional linear power amplifier can consume more current than is necessary at low power output levels. By consuming excessive current at lower power output levels, the conventional linear power amplifier, such as a conventional linear power amplifier used in cellular handsets as well as other wireless devices, can cause an undesirable reduction in battery life.
Thus, there is a need in the art for an effective means for reducing current consumption at low power output levels in a linear power amplifier, such as a linear power amplifier used in a cellular handset.